This report presents a simple and efficient method of layer thinning and p-type doping of WSe 2 with vapor XeF 2 . With this approach, the surface roughness of thinned WSe 2 can be controlled to below 0.7 nm at an etched depth of 100 nm. By selecting appropriate vapor XeF 2 exposure times, 23-layer and 109-layer WSe 2 can be thinned down to monolayer and bilayer, respectively. In addition, the etching rate of WSe 2 exhibits a significant dependence on vapor XeF 2 exposure pressure and thus can be tuned easily for thinning or patterning applications. From Raman, photoluminescence, X-ray photoelectron spectroscopy (XPS), and electrical characterization, a p-doping effect of WSe 2 induced by vapor XeF 2 treatment is evident. Based on the surface composition analysis with XPS, the causes of the p-doping effect can be attributed to the presence of substoichiometric WO x (x < 3) overlayer, trapped reaction product of WF 6 , and nonstoichiometric WSe x (x > 2). Furthermore, the p-doping level can be controlled by varying XeF 2 exposure time. The thinning and p-doping of WSe 2 with vapor XeF 2 have the advantages of easy scale-up, high etching selectivity, excellent controllability, and compatibility with conventional complementary metal-oxide-semiconductor fabrication processes, which is promising for applications of building WSe 2 devices with versatile functionalities.

Sheath and core structure results from secondary hydration and devitrification, initiated at relatively high temperatures during cooling, of the intrusive pitchstone sheets. Less than 0.5% of the water present is an original magma component.

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ADDENDUMin this paper, but halved and idealized, and with the manganese linked with the silicate units.It is owing to their structural similarity that the silicate portion of the infra-red spectrum of roeblingite is related to that of margarosanite.Since submission of this paper, Moore and Shen (1984) have published the crystal structure of roeblingite from Lgmgban, Sweden, using X-ray diffraction data. The silicate portion of the structure was found to be based on [5i309] 6-rings related to those in margarosanite, from which a formula Pb2Ca6(SO,)2(OH)2(H20)4 [Mn(Si309)2] was derived without using any additional analytical data. This formula is similar to that proposed REFERENCE Moore, P. B., and Shen, J. (1984) Am. Mineral. 69, 1173 [Manuscript